1. Field of the Invention
The present invention relates to a recording medium for ink-jet recording, an ink-jet recording method employing the recording medium, and a process for producing the recording medium.
2. Related Background Art
The ink-jet recording system records pictures and letters by discharging fine ink droplets through a nozzle onto a recording medium such as a paper sheet. The ink-jet recording system is characterized by high-speed recording with less noise generation, ease of multicolor recording, needlessness of image development, and other features. The ink-jet recording system is rapidly becoming used widely not only for printers but for information apparatuses such as copying machines, word-processors, facsimile machines, and plotters.
In recent years, digital cameras, digital videos, and scanners have become supplied at low prices, and personal computers have become widely used. As a result, ink-jet recording apparatuses have become widely employed for outputting the picture image information. Therefore, demands have been placed on the ink-jet system output images of high quality, like silver salt type photographs and multicolor gravure prints.
The recording apparatus and the recording system are being improved for higher recording speed. Correspondingly image formation, and full color printing. Correspondingly the recording medium is required to have higher performances.
Under such circumstances, the recording medium is generally required to have the properties below:
(1) high ink-absorption rate with minimum running of the ink,
(2) high density printing with high color development,
(3) high weatherability,
(4) formation of glossy images, and so forth.
Various proposals have been presented to meet such requirements. For example, Japanese Patent Laid-Open No. 59-22683 discloses crack formation on the surface of a printing sheet to improve ink absorption and image gloss, by applying two kinds or more of thermoplastic resin having different minimum film-forming temperatures onto the substrate surface and drying it to form a film.
Japanese Patent Laid-Open Nos. 59-222381, 6-55870, 7-237348, and 8-2090 disclose a thermoplastic resin particle layer formed on the surface of a pigment layer which is transformed into a film after printing.
However, known thermoplastic resins are generally liable to be discolored by exposure to light, and are not suitable for long term storage of the recording sheets or the printed matters.
Furthermore, some kinds of thermoplastic resins have disadvantages in that they do not form a porous layer of desired properties. This causes problems of a low ink absorption rate, extremely small diameter of printed dots causing a white blank of images, insufficient adhesion of the particles to the lower layer or between particles to cause insufficient resistance against scratching, decrease of gloss or deterioration of weatherability on heating for non-porosity, and so forth.
An object of the present invention is to provide a novel recording medium which does not have the aforementioned problems, such as the recording medium not causing discoloration of the recording medium and printed matter, and which forms a printed matter with high ink absorbency and image density.
Another object of the present invention is to provide a process for producing the above novel recording medium.
A further object of the present invention is to provide an ink-jet recording method employing the above recording medium.
The recording medium of the present invention comprises a porous outermost layer on a substrate containing a particulate thermoplastic resin, and the resin exhibiting a xcex94E value of not higher than 20 after light exposure.
The recording method of the present invention comprises allowing ink droplets to fly onto the above recording medium to adhere thereon, and subsequently heating the recording medium as necessary.
The process for producing the recording medium of the present invention comprises forming a porous outermost layer by heat treatment at a temperature not lower than the glass transition temperature but not higher than the minimum film-forming temperature of the particulate thermoplastic resin.